Bare cells isolated have near zero cell discharge, and cold is ideal for long term storage
, even years is fine without topping up. BMS or other parasitic loads are the dangerous wild card.
Personally I would check periodically, more frequently at first until confident, then scale back, eventually to say every other month.
A well insulated box with thermostatically controlled silicone heating
pads at the bottom is the usual solution when needed.
If an easy water heating
system was available then a hydronics solution might be easier.
Yes a long warm-up period is required to ensure the cell interiors match ambient inside the box.
Personally I'd rather design the bank from easily portable units.
There are also systems where the heating elements are part of the battery design.